I think this might be a “yes, but no” kind of thing.
Yes, these are test strips. Yes, they change color to indicate a reading. Yes, they use chemical reactions to cause that color change.
AFAIK: No, these aren’t for testing blood. No, these don’t seem to be for consumption by an electronic meter. And no, I don’t think this is what OP was asking about.
Like, there’s probably some good info, but not for this thread specifically :P
Source: Pulling it straight out of my ass, but it is informed by my limited experience with medical test equipment, and much less limited experience with electronics.
The first example that my brain came up with was definitely Popsicle Toes, and not any children’s song :P